window.onload = function () {
  var oBtn = document.querySelector(".nav-li"); //获取一级菜单元素
  oBtn.onmouseover = function () {
    // this.style.display="none";
    this.querySelector(".dorp-box").style.display = "block";
    //给二级菜单添加阴影
    this.querySelector(".dorp-box").style.boxShadow = " 0 2px 2px gray";
  };
  //鼠标出
  oBtn.onmouseout = function () {
    this.querySelector(".dorp-box").style.display = "none";
    this.querySelector(".dorp-box").style.boxShadow = "none";
  };
};
